This invention relates to an improved oxidation and/or ammoxidation catalyst system containing the elements antimony, uranium, iron and bismuth and to a method for preparing such catalyst system.
It is well known that olefins can be oxidized to oxygenated hydrocarbons such as unsaturated aldehydes and acids, for example, acrolein and methacrolein, acrylic and methacrylic acid. It is also well known that olefins can be ammoxidized to unsaturated nitriles such as acrylonitrile and methacrylonitrile. The value of such oxygenated hydrocarbons and unsaturated nitriles is generally well recognized with acrylonitrile being among the most valuable monomers available to the polymer industry for producing useful polymeric products.
Various catalytic processes are known for the oxidation and/or ammoxidation of olefins. Such processes commonly react an olefin or an olefin-ammonia mixture with oxygen in the vapor phase in the presence of a catalyst. For the production of acrolein and acrylonitrile, propylene is the generally used olefin reactant and for the production of methacrolein and methacrylonitrile, isobutylene is the generally used olefin reactant.
A catalyst system composed of the oxides of antimony and uranium and the oxidation and ammoxidation of olefins using such catalyst has been described in U.S. Pat. Nos. 3,198,750 and 3,308,151. These patents describe preparation of the catalyst by precipitation wherein the oxides of the elements are contained in a slurry which is filtered to remove soluble salts and recover the catalytic components as the filter cake.
In the catalytic oxidation and/or ammoxidation of olefins, the commercial utility of a catalyst system is highly dependent upon the cost of the system, the conversion of the olefin and the yield of the desired product. In many cases a reduction in the cost of a catalyst system in the order of a few pennies per pound or a 1% increase in the yield of a desired product represents a tremendous commercial economical savings. Accordingly, research efforts are continuously being made to define new or improved catalyst systems and methods of making new and old catalyst systems to reduce the cost and/or to upgrade the activity and selectivity of such catalyst systems in particular processes.